1. Field of the Invention
This invention relates to an apparatus for automatically binding any load or pack with a thermally fusible band, preferably a band of paper or like perishable material with a thermally fusible overlay, and more particularly to such an apparatus well calculated to be appended to a rotary printing press for binding successive stacks of printed sheets or signatures, among other applications. The invention also particularly concerns a delivery system of such printed matter or the like incorporating the binding apparatus.
2. Description of the Prior Art
Binding devices using thermally fusible bands are themselves not new but have been known and used for a couple of decades now. Japanese Utility Model Publication No. 46-26480 represents one such conventional device. It comprises a platform or table on which is placed a pack, box, or any other load to be bound. Paid out from its supply reel, a band of fusible plastics material is first loosely looped around the load on the platform and then tightened against the load. Then the band has its lapping parts thermally joined together and is cut off in the neighborhood of the fused joint from its continuous supply.
Both Japanese Patent Publication No. 50-2431 and Utility Model Publication No. 52-2786 suggest delivery systems, with conveyors both upstream and downstream of a binding station of largely foregoing construction. Japanese Patent Publication No. 46-1758, Utility Model Publication No. 4-7043, and Utility Models Nos. 2583319 and 2587225 are hereby cited as each teaching one or more of: (a) a pen for temporary storage of a length of band on its way from supply to binding station; (b) a mechanism for switching the band from one supply reel to another; and (c) a mechanism for swift discharge of the remaining length of old band from the band path around the platform preparatory to band switching from one reel to the other.
All the foregoing citations presuppose use of polypropylene or like fusible plastics bands. More recently, with increasing public awareness of global environment, fusible paper bands have been suggested by Japanese Unexamined Patent Publication No. 2000-177770 for use in substitution for more conventional fusible plastics bands which are nonperishable. By xe2x80x9cfusible paper bandsxe2x80x9d are meant the bands of paper with an overlay of a thermoplastic vinyl adhesive. Lapping parts of each length of such fusible paper band are heated under pressure until they are joined together by the fusion of the thermoplastic overlay.
Japanese Unexamined Patent Publication No. 2000-302104 is a response to this suggestion, teaching a binding device using fusible paper bands. This prior art device represents no substantive improvement over the more conventional ones except for the proposed limitations in temperature, pressure, and heating time to be conformed to in splicing the ends of each length of band.
Fusible paper bands by reason of their makeup demand some extra considerations in use. Creation of fused joints of such bands require relatively large amounts of a thermoplastic vinyl adhesive and, in consequence, correspondingly large quantities of heat, even though the adhesive itself need not be heated to very high temperatures for melting. The heater temperature has therefore been easy to drop greatly each time a fused joint is created. Improper joints have indeed occurred on account of insufficient heater temperature, and hence insufficient melting of the adhesive, in cases where a number of loads are bound in rapid succession, as in newspaper production.
Japanese Utility Model Publication No. 5-45282 teaches to control the magnitude of the electric current energizing the band heater in order to keep the heater temperature constant. This known control system is designed to maintain the heater temperature in the face of variations in the temperature of the environment. The utility model is silent on how to swiftly recover the heater temperature from a drop due to the heating of the fusible paper band.
There are some additional considerations that must be taken into account in use of fusible paper bands. These bands must of necessity be thicker than polypropylene bands for a given degree of strength. For this reason, combined with the presence of the fusible overlay thereon, fusible paper bands are less supple, more rigid, than their plastics counterparts. A further inconvenience is that their surfaces are high in coefficient of friction. All these factors combine to make it difficult for them to travel smoothly along the band guideways in the binding apparatus.
As an additional inconvenience, the thermoplastic overlay on the paper band is easy to come off and adhere to the surfaces defining the band path. Particularly objectionable is the accumulation of the thermoplastic material on the surfaces of the rollers by which the band is fed toward, or pulled back from, the binding station. A slip has actually occurred between the rollers and the band, making it difficult, and even impossible, to feed or tighten the band.
The present invention seeks to expedite the binding of successive loads with fusible paper bands, in particular, through controlled energization of the heater during the operation of the apparatus.
Another object of the invention is to assure smooth travel, either forward or backward, of the fusible paper band along the predefined path from the infeed to the binding station.
A still another object of the invention is to provide a delivery system for newspapers or other loads incorporating the binding apparatus of the above improved constructional and operational characteristics.
Stated in brief, the present invention concerns an apparatus for binding a succession of loads such as stacks of printings with a thermally fusible band. Included is a band looper for loosely looping a band, which is fed continuously from its supply means, around a load so as to provide lapping parts of the band. A band heater is provided for heating the lapping parts of the band for uniting the same into a fused joint after the band has been tightened against the load. The heater is under the control of heater control means whereby the heater is normally energized for a first preassigned period of time at constant intervals during the operation of the apparatus, and at least for a second preassigned period of time, which is longer than the first, in response to the actual heating of the band around each load, after the fusion jointing, in order to compensate for a temperature drop that might occur as a result of heating the band.
Preferably, the heater control means is responsive to a band fusion signal which commands the travel of the band heater to and away from a position for heating the band. Irrespective of being held away from or near the heating position, the heater is intermittently energized for the first preassigned period of time in order to be held at a temperature capable of creating a fused joint for the band. Then, after the band fusion signal is output to dictate the travel of the heater to the heating position, the heater is subsequently energized long enough to have its temperature raised up to approximately the band fusion temperature after the heating of the band.
Experiment has proved that the present invention makes it possible to swiftly recover the heater from an undesired temperature drop due to the heating of the band around each load. The band in use may be either a fusible paper band or any other type of fusible band. With the heater so subjected to a compensatory reheating for each load, any known types of fusible bands can be fused more quickly than heretofore for more efficient binding of the successive loads.
Another aspect of the invention concerns a more comprehensive aspect of the binding apparatus, comprising a platform to which loads to be bound are conveyed one after another, band looper means for loosely looping and releasably holding a thermally fusible band around the load on the platform so as to provide lapping parts of the band, feed means for feeding the band from its continuous supply means to the band looper means, pullback means for pulling back the band that has been loosely looped around the load and which has been released from the band looper means, tightening means for tightening the band against the load, a heater for movable into and out of a space between the lapping parts of the tightened band and hence for thermally uniting them into a fused joint, and cutter means for cutting the band that has been bound around each load, off from the continuous supply means. A heater control means is provided for causing the heater to be normally energized for a first preassigned period of time at constant intervals throughout the course of binding the load and, in response to a band fusion signal commanding the heater to heat the lapping parts of the tightened band into a fused joint, after the fusion jointing, for causing the heater to be energized for at least a second preassigned period of time which is longer than the first, in order to compensate for a temperature drop that might occur as a result of heating the band.
The rollers included in the feed means and the pullback means are provided with doctor blades for making their surfaces clean of the adhesive matter that may adhere thereto from the fusible band. A tightening roller, moreover, which is capable of rotation only in the direction for tightening the band against the load, is provided with means for application of a forced airstream to its surface in order to lessen frictional contact thereof with the remaining length of the band being rapidly withdrawn from the binding apparatus at the time of switching from one band supply reel to another. All these means combine to make the travel, either forward or backward, of the thermally fusible band of any known or suitable type smoother.
The binding apparatus according to the invention may most advantageously be incorporated in a delivery system of, for example, printings from a rotary printing press to a location of shipment such as a truck yard. Such a delivery system may include a stacking station where each preselected number of printings are stacked up. Positioned downstream of the stacking station, a binding station may be constructed as taught by the invention, for binding the successive stacks of printings with a thermally fusible band. Since the stacks can be bound at the binding station far more efficiently than heretofore, such stacks may be formed and delivered to the binding station at a higher rate without the risk of their being held standing by upstream of the binding station.
The above and other objects, features and advantages of this invention and the manner of realizing them will become more apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing the preferred embodiments of the invention.